The invention relates to a device for heating an interior of an electric vehicle by using the waste heat from an air-cooled high-temperature battery.
From German Offenlegungsschrift 26 38 862, it is known in electric vehicles to employ the lead battery also as a heat accumulator. Prior to commencement of the journey, the battery block heats up to an elevated temperature and the stored heat energy is used to heat the vehicle during running. The heat of the battery block can be evacuated by a liquid circuit or by air-cooling of the battery.
Due to their relatively high energy density, so-called "high-temperature batteries" are preferred for planned electric vehicles. Depending on the operating conditions, such batteries must be more or less heavily cooled. In this context, it is known from DE 42 26 781 A1 to provide in the vehicle a heat-carrier circuit with a liquid heat-carrier medium. This arrangement absorbs the waste heat from both the electric drive system and the high-temperature battery, which is linked via a fluid circuit with heat exchanger to the heat-carrier circuit. The waste heat thus absorbed is evacuated via a heat exchanger which is usable as a heating element for the vehicle interior, to the air of the vehicle interior.
One object of the invention is to enable the high-temperature battery of a vehicle to be air-cooled in a manner which is simple and relatively highly reliable. Another object of the invention is to ensure that, in making use of the heat of the air emanating from the battery, a sufficient reduction in temperature is achieved relative to the (in some circumstances) high operating temperature of the battery, the intention being to create an advantageous design in overall terms.
This object is achieved according to the invention in which waste air from the high-temperature battery is conveyed in a controllable manner to a first heat exchanger, which can also be controllably bombarded with fresh air. The first heat exchanger is arranged as part of a water or liquid circuit which has a further heat exchanger for the delivery of heat to air of the interior and is connected, downstream from this further heat exchanger (in the flow direction of the liquid), to heat generating components, e.g. voltage transformer or controller and electric motor, of the electric drive system, to absorb the waste heat from these components.
The invention is based upon the general concept of transferring the heat of the waste air from the high-temperature battery to a water or liquid circuit, so that the high-temperature battery may be reliably air cooled, while the heat of the battery, (in virtually any desired arrangement within the vehicle) is transferred to the interior without significant losses. These advantageous results can be achieved because the liquid flowing in the circuit, particularly water, is capable of transporting large quantities of heat, even with a low quantity of liquid since the, liquid conduits may be insulated with no great effort against heat loss.
The overall design remains desirably uncomplicated, since the liquid circuit, for its part, is also used for heat absorption and hence cooling of heat generating components of the electric drive system. This is readily possible, since the temperature of the liquid, given an appropriate design layout, remains relatively low even during heating operation at maximum power.
Where no heating is required, the liquid circuit can serve solely to cool the components of the electric drive system, since the first heat exchanger, where appropriate, can also be bombarded with fresh air to the extent necessary to evacuate the heat. Moreover, for this purpose, according to a preferred embodiment of the invention, the liquid circuit may be provided with a controllable by-pass duct which bypasses the further heat exchanger, so that the interior, where appropriate, is supplied with no heat whatsoever.
In addition, provision is expediently made to allow air to be led between the battery and the first heat exchanger wholly or partially under circulating-air operation, so that the waste heat from the battery, where appropriate, can be transferred fully into the liquid circuit.
Where appropriate, a further heat accumulator can be disposed in the liquid circuit to provide temporary storage for heat which is not required for heating purposes.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.